The American four-times Wimbledon champion struggled to cope with the windy conditions and Zheng, seeded 25th, served consistently throughout the first set before winning it 7-5 in the tiebreak.

The sixth-seeded Williams finally broke Zheng, Wimbledon semi-finalist in 2008, in the fifth game of the second set and she did so again in the seventh on the way to levelling the match.

Williams, 30, recovered from 0-40 down to hold serve in the fourth game of the third set and she made the decisive break in the 15th game before converting her third match point to set up a last-16 clash with Yaroslava Shvedovaof Kazakhstan.

Shvedova left French Open runner-up Sara Erranired-faced by becoming the first player to win a set in a Grand Slam tournament without conceding a point.

The first set disappeared in a 15-minute blur as Shvedova won 24 consecutive points - known as a golden set - in the third-round match on court three.

Tenth seed Errani fought back in the second but was powerless to stop Shvedova wrapping up a 6-0 6-4 victory.